[time-nuts] Generating a solid PPS from 10Mhz source

Alan Melia alan.melia at btinternet.com
Mon Jan 18 13:33:10 EST 2016


Indeed Bob in the 70s I built a failure diagnostic equipment to record the 
Idd of a chip as a function of a position of a spot of light scanning the 
surface. The intensity was very low and not optimum wavelength.......it was 
a scope raster demagnified by using a microscope camera accessory backwards. 
The intensity was modulated and the signal detected on a PSD and displayed 
on a modified Robot SSTV receiver.....but it showed just how senstive chips 
are to light.

Alan
G3NYK

----- Original Message ----- 
From: "Bob Camp" <kb8tq at n1k.org>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Monday, January 18, 2016 3:11 PM
Subject: Re: [time-nuts] Generating a solid PPS from 10Mhz source


> Hi
>
> Back in the 70’s I was involved in making LCD watches. The whole “photo”
> issue had not been fully through through. One day our chief marketing guy 
> for
> the project was driving around in Phoenix AZ. He looks down and notices 
> that
> his watch is dead. Pops out a spare, puts it on, confirms it it working. 
> Hangs his arm out
> the window and …. that one is dead as well.
>
> We changed the die coat on the ASIC to an opaque version soon after that …
>
> Light does indeed interact with semiconductors. It happens even on 
> circuits that
> you would not *think* are photo sensitive. Physics is nasty that way ….
>
> Bob
>
>> On Jan 18, 2016, at 6:45 AM, Poul-Henning Kamp <phk at phk.freebsd.dk> 
>> wrote:
>>
>> --------
>> In message <569BC23A.3030400 at arcor.de>, Gerhard Hoffmann writes:
>>
>>> LEDs abused as References:
>>
>> This is one of the most stupid ideas ever, because LEDs works both ways.
>>
>> (Back when LED wrist-watches first came out, people soon discovered
>> that they would reset themselves when photographed with flash.)
>>
>> If you insist on using LEDs as voltage references, the first thing
>> you need to do is to dip the LED in something which shields it 100%
>> from incoming light *including infrared*
>>
>> -- 
>> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
>> phk at FreeBSD.ORG         | TCP/IP since RFC 956
>> FreeBSD committer       | BSD since 4.3-tahoe
>> Never attribute to malice what can adequately be explained by 
>> incompetence.
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